Circular stapler and staple head assembly thereof

ABSTRACT

A circular stapler and a staple head assembly thereof are disclosed. The staple head assembly comprises a staple barrel assembly and an anvil assembly. The anvil assembly includes an anvil ring and an anvil shaft which are fixedly connected to each other, where the anvil shaft is capable of sliding along the longitudinal direction in an anti-expansion tube. The staple barrel assembly includes a staple barrel, a staple pusher piece arranged within the staple barrel and a staple cartridge fixed at a distal end of the staple barrel.

TECHNICAL FIELD

The invention relates to a circular stapler and, more particularly, to astaple head assembly of a circular stapler, which belongs to thetechnical field of medical instrument.

BACKGROUND

It has been a history of more than 4,000 years for people to get thecognition of hemorrhoid. Up to now, the conventional methods fortreating internal hemorrhoid include injection sclerotherapy, rubberband ligation and various kinds of surgical excisions. All these methodsare treatments against the hemorrhoid per se and intended to make thehemorrhoid dwindled or disappeared. Among surgical excisions ofhemorrhoid, a method named PPH surgery is to perform a procedure forprolapse and hemorrhoids with the assistance of a circular stapler.

U.S. Pat. No. 6,083,241 discloses a circular stapler, as shown in FIG.1, its staple head assembly 40 includes an anvil 60 and a staple barrel41 provided with a staple cartridge, a staple pusher and staples inside,and the anvil 60 and the staple barrel 41 are disposed oppositely.During surgery, the hemorrhoidal mucosa is pulled into the staple barrel41, and is cut annularly while the anastomosis is performed between theanvil 60 and staple barrel 41. The opening on the housing of staplebarrel 41 is significantly small, which can only be served to form apassageway 42 for string guiding instrument 140 to pass through thestaple barrel 41 and to pull the purse-string sutured tissue into thestaple barrel 41.

Currently, the staple barrel of commonly-used circular stapler, as thelimitations in its structure, may provide limited viewing window andoperating space for surgeon during the using process in surgery, whichis bad for pulling-in operation on tissues. Besides, the accommodatingspace of staple barrel is also too limited to accommodate moreto-be-excised tissues, which has great limitations, while a plurality ofhemorrhoids need to be cut at one time in surgery (such as TST surgeryagainst a plurality of hemorrhoids).

In addition, according to the clinical experience of surgeons, if anoverlong tissue is pulled into the staple barrel, the postoperativeperformance may be not well. For example, it can be learned from medicalknowledge that: a dentate annular line which can be seen at thecommissure of anal canal skin and rectal mucosa and is enclosed by theedge of anal valves and the lower end of anal columns, is named dentateline. As the tissue structure above and below the dentate line aredifferent, more than 85% of rectum and anus diseases occur near thedentate line. The dentate line is an induction area of defecationreflex, so when the excrement arrives at the anal canal via the rectum,the nerve terminal receptor at dentate line area will be stimulated andthen make the anal canal open reflectively to discharge the excrement.If the tissues pulled in are too long to lead to excise dentate line insurgery, it will cause decreased defecation reflex on postoperativepatient, which may make some adverse reactions such as constipation orsensory fecal incontinence occurred.

However, the conventional circular stapler only has scale indication forindicating the depth of stapler into anus on the outer surface of staplebarrel (such as reference numeric 49 in FIG. 1), which can't providecriterion for surgeon to estimate the amount of hemorrhoid mucosatissues pulled into staple barrel. As a result, the amount and depth ofmucosa tissues pulled into staple barrel cannot be determined, which maycause too many tissues pulled into staple barrel to make poorpostoperative performance on patients.

SUMMARY

An object of the invention is to provide a circular stapler and thestaple head assembly thereof, which can obtain large view window, largecapacity and high operation convenience.

Another object of the invention is to provide a circular stapler and thestaple head assembly thereof, which have the indicator function forindicating the depth of to-be-excised tissues pulled in to avoid toomany tissues to be pulled in.

The object of the invention is realized by the technical solutions asfollows:

A staple head assembly of circular stapler, comprising:

a staple barrel assembly including a staple barrel, a staple pusherarranged inside said staple barrel and a staple cartridge fixed at adistal end of said staple barrel; the distal end of said staple barrelassembly being a staple cartridge surface; said staple barrel comprisinga tubular housing, an anti-expansion tube disposed in said housing and astiffener connected between said housing and said anti-expansion tube;said housing being provided with a first cavity for accommodatingto-be-excised tissues, and a proximal end of said housing beingconfigured for connecting with a body of said circular stapler, and adistal end of said housing being configured for mounting said staplecartridge; wherein, at least one opening communicating with said firstcavity is arranged on sidewall of said housing of staple barrel, and adistance from a distal end of said anti-expansion tube to said staplecartridge surface is larger than that from a distal end of said openingto said staple cartridge surface, and at least a part of said firstcavity is exposed from said opening; and

an anvil assembly including an anvil ring and an anvil shaft which arefixedly connected to each other, said anvil shaft being capable ofsliding in said anti-expansion tube along a longitudinal direction.

Preferably, said housing comprises a first part with the distal end ofhousing and a second part with the proximal end of housing, and adiameter of said first part is larger than that of said second part, anda proximal end of said first part is connecting to a distal end of saidsecond part in a tapered way.

Preferably, said housing of staple barrel is provided with a pluralityof openings symmetrical about the longitudinal axis of said housing, andone said stiffener is correspondingly disposed between every twoadjacent openings.

Preferably, in the cross-section of said housing of staple barrel, acircular arc length of said opening is larger than that of a connectingportion between two adjacent openings.

Preferably, the proximal end of said anti-expansion tube extends to beclose to the proximal end of said housing, and the proximal end of saidanvil shaft which is adaptable with said anti-expansion tube alsoextends to be close to the proximal end of said housing.

Preferably, the distance from the distal end of said anti-expansion tubeto said staple cartridge surface is less than that from the proximal endof said opening to said staple cartridge surface, and the distance fromthe proximal end of said anti-expansion tube to said staple cartridgesurface is larger than that from the proximal end of the opening to saidstaple cartridge surface.

Preferably, at least one guiding slot is arranged in a through-hole ofsaid anti-expansion tube, and said anvil shaft is provided with at leastone guiding rib accordingly, which is capable of sliding in said guidingslot.

Preferably, said stiffener extends along the longitudinal direction fromthe proximal end of said anti-expansion tube to beyond the distal end ofsaid anti-expansion tube and to be close to said staple cartridge.

Preferably, the shape of said staple pusher is made to be adaptable withsaid staple barrel, and a second cavity arranged inside said staplepusher is aligned with said first cavity of said staple barrel.

Preferably, said staple pusher comprises: a pusher ring at the distalend; a plurality of supporting plates extending along the longitudinaldirection from said pusher ring to the proximal end in a tapered way;and a plurality of insertion sheets in long-stripe shape which areconnected between two adjacent supporting plates and separated from eachother; wherein said plurality of supporting plates are engaged with thecorresponding said stiffeners and arranged to form said second cavity,and said plurality of insertion sheets in long-stripe shape arerespectively inserted to an insertion space which is enclosed by saidanti-expansion tube, said housing and two adjacent stiffeners.

Preferably, the distance from the distal end of said insertion sheets tosaid staple cartridge surface is larger than that from the distal end ofsaid opening to said staple cartridge surface, and at least a part ofsecond cavity is exposed from said opening.

Preferably, the distance from the distal end of said opening to saidstaple cartridge surface is less than or equal to 32 mm.

Preferably, the distance from the distal end of said opening to saidstaple cartridge surface is larger than or equal to 20 mm, and less thanor equal to 32 mm.

Preferably, the distance from the distal end of said opening to saidstaple cartridge surface is 30 mm.

Preferably, the distal end of said opening is provided with an indicatorline.

A circular stapler, comprising a body and a staple head assemblyconnected with the distal end of said body, where the staple headassembly is as above described.

Compared with the prior art, beneficial effects of the embodiments ofthe invention mainly include:

1) by arranging opening(s) which can be communicating with the firstcavity of the staple barrel in the staple barrel, with the distance fromthe distal end of the anti-expansion tube to the staple cartridgesurface being larger than that from the distal end of the opening(s) tothe staple cartridge surface, at least a part of first cavity can beexposed from the opening(s), which can thusly not only provide a largerview window during surgery, but also facilitate the pulling-in operationon tissues and accommodate more to-be-excised tissues;

2) the distance from the distal end of the opening(s) of the staplebarrel to the staple cartridge surface is less than or equal to 32 mm,which can thusly allow the surgeon to take the distal end of theopening(s) as a criterion determining the depth of tissues pulled induring surgery to avoid too long tissues pulled in to affect the surgeryeffect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a circular stapler and a string guidinginstrument in prior art;

FIG. 2 is an exploded view of the staple head assembly of circularstapler provided by the first embodiment of the present invention;

FIG. 3A is an assembled view of the staple head assembly of circularstapler provided by the first embodiment of the present invention;

FIG. 3B is a sectional assembled view of the staple head assembly ofcircular stapler provided by the first embodiment of the presentinvention;

FIG. 4A is a perspective view of the staple barrel provided by the firstembodiment of the present invention;

FIG. 4B is a front view of the staple barrel provided by the firstembodiment of the present invention;

FIG. 4C is a top view of the staple barrel provided by the firstembodiment of the present invention;

FIG. 4D is a bottom view of the staple barrel provided by the firstembodiment of the present invention;

FIG. 4E is a A-A sectional view of the staple barrel provided by thefirst embodiment of the present invention;

FIG. 4F is a B-B sectional view of the staple barrel provided by thefirst embodiment of the present invention;

FIG. 5A is a perspective view of the staple pusher provided by the firstembodiment of the present invention;

FIG. 5B is a front view of the staple pusher provided by the firstembodiment of the present invention;

FIG. 5C is a top view of the staple pusher provided by the firstembodiment of the present invention;

FIG. 6 is a schematic diagram showing the operational state of thestaple head assembly in surgery provided by the first embodiment of thepresent invention; and

FIG. 7 is a perspective view of the staple head assembly provided by thesecond embodiment of the present invention.

Wherein, reference numerals are illustrated hereinbelow:

THE INVENTION

body 1

staple head assembly 2

staple barrel assembly 3

-   -   staple barrel 31, 31′        -   tubular housing 311            -   first cavity 310, first part 311 a, second part 311 b,            -   distal end 311 c, proximal end 311 d        -   opening 313: distal end 313 c, proximal end 313 d, arc            length 313 a        -   connecting portion 314: arc length 314 a        -   anti-expansion tube 315            -   distal end 315 c, proximal end 315 d            -   through-hole 3151, guiding slot 3152        -   stiffener 316        -   insertion space 317    -   staple cartridge 32        -   staple cartridge surface 320    -   staple pusher 33, 33′        -   second cavity 330        -   pusher ring 331        -   supporting plate 332, 332′            -   slot 3321, proximal edge 3322, 3322′        -   insertion sheet 333

anvil assembly 5

-   -   anvil ring 51    -   anvil shaft 52, guiding rib 521

to-be-excised hemorrhoid tissues 7

anoscope 8

indicator line 9

PRIOR ART

staple head assembly 40

anvil 60

staple barrel 41

passageway 42

string guiding instrument 140

DETAILED DESCRIPTION

Hereinafter, embodiments are described in detail with reference to theaccompanying drawings. The term “distal end” and “proximal end” used inthe description are described relative to the position of surgeon,wherein, the “distal end” is the end away from surgeon, and the“proximal end” is the end close to surgeon, which is opposite to thedistal end.

The First Embodiment

As shown in FIG. 2, FIG. 3A and FIG. 3B, a circular stapler, provided bythe embodiment of the present invention, comprises a body 1, a firstactuating mechanism (not shown) and a second actuating mechanism (notshown) which are arranged on the body 1, and a staple head assembly 2connected to the distal end of body 1.

The staple head assembly 2 of the embodiment of the invention at leastincludes a staple barrel assembly 3 and an anvil assembly 5 which aredisposed oppositely. The anvil assembly 5 includes an anvil ring 51 andan anvil shaft 52 which are fixedly connected to each other. The anvilassembly 5 may be driven by the first actuating mechanism (not shown) tomove along the longitudinal direction of circular stapler relative tothe staple barrel assembly 3, between a first position away from thestaple barrel assembly 3 and a second position close to the staplebarrel assembly 3. When the anvil assembly 5 is in the first position,it is convenient for pulling the to-be-excised tissues into the staplebarrel 31, and when the anvil assembly 5 is in the second position, thetissues in the staple barrel 31 can be stapled and excised.

The staple barrel assembly 3 at least includes a staple barrel 31, astaple cartridge 32 fixed at the distal end of staple barrel 31, and astaple pusher 33 arranged inside the staple barrel 31. The staple pusher33 moves along the longitudinal direction of circular stapler with thefunction of the second actuating mechanism, to fire the staples instaple cartridge 32 to the to-be-excised tissues in staple barrel 31,which can get the tissues stapled and sutured. The staple cartridge 32is fixed at the distal end of staple barrel 31, thereby the distal endsurface of the staple barrel assembly 3 is the staple cartridge surface320, which is disposed oppositely as to the anvil ring 51.

As shown in FIG. 4A to FIG. 4F, the staple barrel 31 includes a tubularhousing 311, an anti-expansion tube 315 disposed in the tubular housing311 and a stiffener 316 connected between the tubular housing 311 andthe anti-expansion tube 315. Preferably, in this embodiment, the tubularhousing 311, the anti-expansion tube 315 and the stiffener 316 areintegrally molded.

The housing 311 includes a first cavity 310 for accommodating theto-be-excised tissues. The distal end 311 c of housing 311 is configuredfor mounting the staple cartridge 32, and the proximal end 311 d ofhousing 311 is configured for connecting the body 1 of circular stapler.Preferably, in this embodiment, the housing 311 includes a first part311 a provided with the distal end 311 c of housing and a second part311 b provided with the proximal end 311 d of housing. The diameter ofthe first part 311 a is larger than that of the second part 311 b, andthe proximal end of the first part 311 a is connected to the distal endof the second part 311 b in a tapered way.

At least one opening 313 communicating with the first cavity 310 isarranged on the sidewall of said housing 311, which is for surgeons toobserve the situation of tissues pulled-in. Preferably, in thisembodiment, the sidewall of housing 311 of staple barrel 31 is providedwith four openings 313 symmetrical about the longitudinal axis ofhousing 311, as a result that the openings 313 in four directions mayprovide better multi-direction windows for medical workers duringsurgery. Of course, the amount of openings 313 are not limited thereof,and it may also be one, two, three or more. In the cross-section of thehousing of the staple barrel 31, the circumferential arc length 313 acorresponding to the opening 313 is larger than the circumferential arclength 314 a corresponding to the connecting portion 314 between twoadjacent openings. Thus, such large openings may provide the surgeonexcellent viewing angle during surgery. Preferably, in this embodiment,as shown in FIG. 4B and FIG. 4D, the circumferential arc lengthcorresponding to each opening 313 is roughly equal to ¼ ofcircumferential length of the housing 311.

The anti-expansion tube 315 includes a through-hole 3151 to allow theanvil shaft 52 of anvil assembly 5 to slide through. In a preferredembodiment, the through-hole 3151 of anti-expansion tube 315 is disposedwith two guiding slots 3152 therein (as shown in FIG. 4D and FIG. 4E),and the anvil shaft 52 is provided with two guiding ribs 521 (as shownin FIG. 2), each of which may slide in the corresponding guiding slots3152. The number of pairs of guiding slot and guiding rib may be notlimited to two, and it can be one or more than two. To accommodate moreto-be-excised tissues within the housing 311 and provide largeroperating space for the instruments such as the string guidinginstrument to facilitate the pulling-in operation of tissues, thedistance from the distal end 315 c of anti-expansion tube 315 to thestaple cartridge surface 320 is larger than that from the distal end 313c of opening 313 to the staple cartridge surface 320, that is to say,the distance from the distal end 315 c of anti-expansion tube 315 to theproximal end 311 d of housing 311 is less than that between the farthestedge (that is the distal end) 313 c of opening 313 and the proximal end311 d of housing 311, thus at least a part of first cavity 310 isexposed from the opening 313. Preferably, in this embodiment, thedistance from the distal end 315 c of anti-expansion tube 315 to thestaple cartridge surface 320 is less than that from the proximal end 313d of opening 313 to the staple cartridge surface 320, and the distancefrom the proximal end 315 d of anti-expansion tube 315 to the staplecartridge surface 320 is larger than that from the proximal end 313 d ofopening 313 to the staple cartridge surface 320. Such structure isbenefit for the sliding stability of the anvil shaft 52 sliding in theanti-expansion tube 315 along a longitudinal direction. However, theinvention is not limited thereto, for example, the anti-expansion tubein whole may also correspond to the second part of the housing, that isthe distance from the distal end of anti-expansion tube to the staplecartridge surface is larger than that from the proximal end of openingto the staple cartridge surface.

Both the distal ends of the stiffener 316 and the anti-expansion tube315 in present invention are relatively lower than those in prior art inwhich both the distal ends of stiffener and anti-expansion tube areclose to the staple cartridge surface. To compensate for shortage inaxial and circumferential strength resulted by lowering ofanti-expansion tube 13, the proximal end 315 d of anti-expansion tube315 in the invention is made to extend as compared with that in priorart, and also the anvil shaft 52 is lengthened (which equals to anextension of proximal end) to increase the adaption and connectionbetween the anvil shaft 52 and the anti-expansion tube 315. To bespecific, the proximal end 315 d of anti-expansion tube 315 extends tobe close to the proximal end 311 d of housing 311, and the proximal endof anvil shaft 52 being adaptable with the anti-expansion tube 315 alsoextends to be close to the proximal end 311 d of the housing 311.

The stiffener 316 is mainly served for connecting the tubular housing311 and the anti-expansion tube 315. In this preferred embodiment, sincethe housing 311 is provided with a plurality of openings 313, along-plane-shaped stiffener 316 can be arranged correspondingly on theinner wall of the connecting portion 314 which is mounted between twoadjacent openings on the housing 311, to fix the anti-expansion tube 315in the housing 311 correspondingly. Among the anti-expansion tube 315,the housing 311 and two adjacent stiffeners 316, there is an insertionspace 317 enclosed (as shown in FIG. 4C) for the insertion sheet 333 ofthe staple pusher 33 (illustrated hereinafter) to insert into. In thispreferred embodiment, the stiffener 316 extends from the proximal end315 d of the anti-expansion tube 315 along the longitudinal direction tobeyond the distal end 315 c of anti-expansion tube 315, and to get closeto the staple cartridge 32. That is, the proximal end of stiffener 316is basically aligned with the proximal end 315 d of anti-expansion tube315, however the distal end of the stiffener 316 extends to be moreclose to the staple cartridge surface 320 than the distal end 313 c ofthe opening 313. Such arrangement is benefit for improving the strengthof the housing 311 of staple barrel 31. The amount, length and placementof the stiffeners may be varied in many ways. For example, eachstiffener may be placed on the outer wall of the anti-expansion tubecontinuously or discontinuously.

As shown in FIG. 5A to FIG. 5C, the shape of staple pusher 33 may bemade to match with the staple barrel 31. Specifically, the staple pusher33 includes: a pusher ring 331 at the distal end, a plurality ofsupporting plates 332 extending from the pusher ring 331 to the proximalend along the longitudinal direction in a tapered way, and a pluralityof long-striped insertion sheet 333 connected between two adjacentsupporting plates 332 and separated from each other. In the staplepusher 33, there is a second cavity 330 (that is an inner space which isformed by being embraced with a plurality of supporting plates 332),which is aligned to the first cavity 310 of staple barrel 31. Aplurality of long-striped insertion sheet 333 are inserted into theinsertion space 317 of staple barrel 31 to form a tubular like structuresurrounding around the periphery of anti-expansion tube 315. In thispreferred embodiment, to accommodate more to-be-excised tissues andprovide larger operating space for the instrument such as the stringguiding instrument to facilitate the pulling-in operation of tissues,similar with the corresponding structure of anti-expansion tube 315, thedistance from the distal end of insertion sheet 333 to the staplecartridge surface 320 is larger than that from the distal end of opening313 to the staple cartridge surface 320, and at least a part of secondcavity 330 is exposed from the opening 313.

Each supporting plate 332 corresponds to each stiffener 316 in thestaple barrel 31, and each supporting plate 332 is provided with a slot3321 capable of engaging on the outside surface of the stiffener 316correspondingly. The engaging way between the stiffener and thesupporting plate may be changed to: the stiffener of the staple barrelis provided with a slot, and the supporting plate of staple pusher canbe engaged into the slot of the stiffener. The engaging fixation waybetween the stiffener and the supporting plate is benefit for improvingthe stableness of the staple pusher 33 in the staple barrel 31.Obviously, the stiffener and the supporting plate may employ otherfixation way. In addition, in this embodiment, after the supportingplate 332 of staple pusher 33 and the stiffener 316 of staple barrel 31are assembled, the proximal edge 3322 of the supporting plate 332 abutsagainst the inner side of the housing 311 of staple barrel 31.

Hereinafter, taking the surgery of excising hemorrhoid tissues forexample, the operating method of the circular stapling instrument inthis embodiment of the invention will be illustrated with FIG. 6 as:after a purse-string suture is performed on the to-be-excised hemorrhoidtissues 7, place the circular stapler which is under the condition thatthe anvil ring 51 and the staple cartridge 32 are far away from eachother into an anoscope 8; afterwards, apply the string guidinginstrument to insert into the space between the anvil ring 51 and thestaple cartridge 32 from the opening 313 of staple barrel 31 and to pullthe purse string to get the to-be-excised hemorrhoid tissues 7 pulledinto the accommodating space (the first cavity and the second cavity) ofcircular stapler; and then, adjust the first actuating mechanism ofcircular stapler to make the distance from the staple cartridge 32 tothe anvil ring 51 reduced until the anvil ring 51 and the staplecartridge 32 clap the to-be-excised hemorrhoid tissues 7 tightly;subsequently, operate the second actuating mechanism of circular staplerand fire the staple in the staple cartridge 32 to the tissues by usingthe staple pusher 33 to perform stapling and suturing and to excise thetissues at the same time. The application of the circular stapler inthis embodiment of the invention is not limited to excise the hemorrhoidtissues, but also may be used to excise other tissues in the anorectalsurgery.

Second Embodiment

As shown in FIG. 7, one difference from the first embodiment is, in thestaple barrel 31′ of second embodiment, one end of opening 313 (thedistal end or edge of opening) close to the staple cartridge surface 320is provided with an indicator line 9, which is convenient for thesurgeon with different models of circular stapler to get to know thevalue of distance L from the distal end of opening to the staplecartridge surface. The distance L from the indicator line 9 to thestaple cartridge surface 320 may be, for example, greater than or equalto 20 mm, and less than or equal to 32 mm, and preferable it can be 30mm to obtain the best clinical effect. The indicator line 9 may berealized in various ways, which includes directly printing the indicatorline at the opening of the staple barrel 31′ and marking thecorresponding distance value such as 20 mm, 30 mm or 32 mm and so on.Thusly, before the surgery, the surgeon may know the distance from theopening to the staple cartridge surface in such stapler according to thevalue indicated by the indicator line 9. During the operation process ofsurgery, the doctor may take the distal end of opening in the staplebarrel as a criterion determining the depth of tissues pulled in toavoid too long tissues pulled in to affect the surgery effect.

The other difference from the first embodiment is, the proximal edge3322′ of supporting plate 332′ of staple pusher 33′ may not abut againstthe housing 311 of staple barrel 31′.

The above description only illustrates preferred embodiments of theinvention, which can't be used for limiting the scope of the invention.Therefore, any other equivalent deformations or modifications withoutdeparting from the spirit of the invention are intended to be includedin the scope of invention.

What is claimed is:
 1. A staple head assembly of circular stapler,comprising: a staple barrel assembly including a staple barrel, a staplepusher arranged inside said staple barrel and a staple cartridge fixedat a distal end of said staple barrel; the distal end of said staplebarrel assembly being a staple cartridge surface; said staple barrelcomprising a tubular housing, an anti-expansion tube disposed in saidhousing and a stiffener connected between said housing and saidanti-expansion tube; the staple pusher being movable relative to thetubular housing, the anti-expansion tube and the stiffener being notmovable relative to the tubular housing; said housing being providedwith a first cavity for accommodating to-be-excised tissues, and aproximal end of said housing being configured for connecting with a bodyof said circular stapler, and a distal end of said housing beingconfigured for mounting said staple cartridge; wherein, at least oneopening communicating with said first cavity is arranged on sidewall ofsaid housing of staple barrel, and a distance from a distal end of saidanti-expansion tube to said staple cartridge surface is larger than thatfrom a distal end of said opening to said staple cartridge surface, andat least a part of said first cavity is exposed from said opening; andan anvil assembly including an anvil ring and an anvil shaft which arefixedly connected to each other, said anvil shaft being capable ofsliding in said anti-expansion tube along a longitudinal direction,wherein said housing of staple barrel is provided with a plurality ofopenings symmetrical about the longitudinal axis of said housing, andone said stiffener is correspondingly disposed between every twoadjacent openings; wherein in the cross-section of said housing ofstaple barrel, a circular arc length of said opening is larger than thatof a connecting portion between two adjacent openings.
 2. The staplehead assembly of circular stapler according to claim 1, wherein saidhousing comprises a first part with the distal end of housing and asecond part with the proximal end of housing, and a diameter of saidfirst part is larger than that of said second part, and a proximal endof said first part is connecting to a distal end of said second part ina tapered way.
 3. The staple head assembly of circular stapler accordingto claim 1, wherein the distance from the distal end of saidanti-expansion tube to said staple cartridge surface is less than thatfrom the proximal end of said opening to said staple cartridge surface,and the distance from the proximal end of said anti-expansion tube tosaid staple cartridge surface is larger than that from the proximal endof the opening to said staple cartridge surface.
 4. The staple headassembly of circular stapler according to claim 1, wherein at least oneguiding slot is arranged in a through-hole of said anti-expansion tube,and said anvil shaft is provided with at least one guiding ribaccordingly which is capable of sliding in said guiding slot.
 5. Thestaple head assembly of circular stapler according to claim 1, whereinsaid stiffener extends along the longitudinal direction from a proximalend of said anti-expansion tube to beyond the distal end of saidanti-expansion tube and to be close to said staple cartridge.
 6. Thestaple head assembly of circular stapler according to claim 1, whereinthe shape of said staple pusher is made to be adaptable with said staplebarrel, and a second cavity arranged inside said staple pusher isaligned with said first cavity of said staple barrel.
 7. The staple headassembly of circular stapler according to claim 1, wherein the distancefrom the distal end of said opening to said staple cartridge surface isless than or equal to 32 mm.
 8. The staple head assembly of circularstapler according to claim 7, wherein the distance from the distal endof said opening to said staple cartridge surface is larger than or equalto 20 mm, and less than or equal to 32 mm.
 9. The staple head assemblyof circular stapler according to claim 8, wherein the distance from thedistal end of said opening to said staple cartridge surface is 30 mm.10. The staple head assembly of circular stapler according to claim 1,wherein the distal end of said opening is provided with an indicatorline for indicating a distance value from the distal end of said openingto said staple cartridge surface.
 11. A circular stapler, comprising: abody; and a staple head assembly according to claim 1, connected withthe distal end of said body.
 12. The circular stapler according to claim11, wherein said housing comprises a first part with the distal end ofhousing and a second part with the proximal end of housing, and adiameter of said first part is larger than that of said second part, anda proximal end of said first part is connecting to a distal end of saidsecond part in a tapered way.
 13. The circular stapler according toclaim 11, wherein said housing of staple barrel is provided with aplurality of openings symmetrical about the longitudinal axis of saidhousing, and one said stiffener is correspondingly disposed betweenevery two adjacent openings.
 14. The circular stapler according to claim13, wherein, in the cross-section of said housing of staple barrel, acircular arc length of said opening is larger than that of a connectingportion between two adjacent openings.
 15. The circular stapleraccording to claim 11, wherein the distance from the distal end of saidanti-expansion tube to said staple cartridge surface is less than thatfrom the proximal end of said opening to said staple cartridge surface,and the distance from the proximal end of said anti-expansion tube tosaid staple cartridge surface is larger than that from the proximal endof the opening to said staple cartridge surface.
 16. The circularstapler according to claim 11, wherein at least one guiding slot isarranged in a through-hole of said anti-expansion tube, and said anvilshaft is provided with at least one guiding rib accordingly which iscapable of sliding in said guiding slot.
 17. The circular stapleraccording to claim 11, wherein said stiffener extends along thelongitudinal direction from a proximal end of said anti-expansion tubeto beyond the distal end of said anti-expansion tube and to be close tosaid staple cartridge.
 18. The circular stapler according to claim 11,wherein the shape of said staple pusher piece is made to be adaptablewith said staple barrel, and a second cavity arranged inside said staplepusher piece is aligned with said first cavity of said staple barrel.19. The circular stapler according to claim 11, wherein the distancefrom the distal end of said opening to said staple cartridge surface isless than or equal to 32 mm.
 20. The circular stapler according to claim19, wherein the distance from the distal end of said opening to saidstaple cartridge surface is larger than or equal to 20 mm, and less thanor equal to 32 mm.
 21. The circular stapler according to claim 20,wherein the distance from the distal end of said opening to said staplecartridge surface is 30 mm.
 22. The circular stapler according to claim11, wherein the distal end of said opening is provided with an indicatorline for indicating a distance value from the distal end of said openingto said staple cartridge surface.